The inhibition of farnesyl transferase, and consequently of the farnesylation of the ras protein, blocks the capacity of the mutated ras protein to transform normal cells into cancerous cells.
The C-terminal sequence of the ras gene contains the unit "CAAX" or "Cys-Aaa.sub.1 -Aaa.sub.2 -Xaa", in which Aaa represents an aliphatic amino acid and Xaa represents any amino acid.
It is known that tetrapeptides with a CAAX sequence can inhibit the farnesylation of the ras protein. For example, peptide inhibitors of farnesyl transferase, Cys-Aaa.sub.1 -Aaa.sub.2 -Xaa, which are more particularly represented by the peptides Cys-Val-Leu-Ser, Cys-Val-Ile-Met and Cys-Val-Val-Met which manifest their inhibitory activity at concentrations in the region of 10.sup.-6 M or 10.sup.-7 M, have been described in PCT Application WO 91/16340 and in Application EP 0,461,869.